An empirical study of antenna characteristics toward RF-based localization for IEEE 802.15.4 sensor nodes

Localization using the characteristics of the Radio Frequency (RF) in wireless sensor networks is attractive because the method does not require additional measuring devices, and hence satisfies low cost and low power consumption needs. The range information derived from Received Signal Strength (RSS), which attenuates over the distance and node connectivity, is, however, inaccurate and unpredictable in the real world due to problems caused by sensor motes and the environment of the sensor field. In this paper, through an empirical analysis, we present detailed radio signal properties of the 2.4GHz IEEE 802.15.4 radio module. We also provide the methodology of antenna design and mounting to alleviate the antenna orientation and RSS fluctuation problems, which are key factors that make RF-based ranging irregular in an obstacle-free environment. Our work is differentiated from previous work, which concludes with merely revealing the problems, ignoring them by assumptions, or even limiting the feasibility of RF utilization in localization.